The Colorado Sun originally published this story on Nov 24, 2025. It was updated on Nov 25, 2025.
A 54-year-old hiker’s fatal fall into an abandoned mine shaft near Ouray last month highlights a broader danger left behind by Colorado’s rich mining history: more than 23,000 inactive mining sites, many of which are still unmarked, unsecured or unknown to the state.
Colorado has closed about 14,000 abandoned mine openings since 1980, but officials say thousands more remain. Erosion, vegetation and shifting terrain have obscured decades-old mine features, making it difficult for the state to track them and even harder for hikers and recreationalists to spot hazards before it’s too late.
“Obviously that leaves a lot more than we think are out there. Some we know about, some we certainly do not just because in these historic mining areas, time changes things as well,” said Jeff Graves, program manager for Colorado’s Inactive Mining Reclamation Program.
“A feature may not be visible at the surface because it was covered in timber and over time that timber rots and suddenly now there’s a new feature or the ground collapses and something exposes its surface,” he said.
The state was unaware of the 8-foot-wide mine shaft near Spirit Gulch in the Uncompahgre National Forest before Jennifer Nelson, of Ridgway, fell to her death while hiking with dogs Oct. 20, Graves said.
After she was reported missing on a Monday evening, rescuers found her body the following morning in a deep, water-filled pit about 50 feet off the mining road, the Ouray Plaindealer reported. The dogs stayed nearby and were silently watching the volunteers, according to the newspaper.
Historically, more rescues have been along the Front Range, which Graves attributes to the higher population in closer proximity to historic mining sites, but the state doesn’t keep record of the number of mine-related accidents or fatalities across the state.
Nelson, who served on Ridgway’s planning commission, was hiking in an area above the historic Idarado Houses, which is a popular spot for hikers, especially in the summer with three wildflower-filled basins and views of the Red Mountains. It is accessed via an old gated mining road and has ruins of the Barstow and Greyhound mines.
There was no visible cue, like a rock pile, that there was a shaft nearby, Graves said.
“When my project manager went out to the site … he had to walk kind of uphill a good bit to get to where the mine feature was,” Graves said. “He said it would have been pretty easy to potentially come upon that without recognizing it if you were focused on something uphill or not directly paying attention to what was right in front of you or coming down the hill, it could have been a potential hazard.”
Mine shafts, which are vertical openings, are the No. 1 cause of death and injury in abandoned mines, according to the state. Debris, rotten timber and false floors can hide vertical openings.
Other horizontal mining features, like tunnels, can often have unstable roofs or low oxygen levels, Graves said.
Victims of mining accidents have fallen down holes that opened up under their weight, drowned in near-freezing pools of water at the bottom of shafts, have been buried in unpredictable cave-ins from loose rock and encountered deadly odorless gases.
“The horizontal ones I think become more enticing for folks because it doesn’t appear like there’s a hazard,” he said. “But those hazards are sometimes difficult to visualize or even see.”
Nelson’s cause of death is still being investigated by the county coroner’s office, Ouray County Sheriff’s Office and Colorado Bureau of Investigation.
Colorado’s Division of Reclamation, Mining and Safety has two lists of incidents dating back to the 1950s on rescues and fatalities in abandoned mining sites, compiled from state records and search and rescue organizations.
One outdated list, on the DRMS website, estimates 18 people have died inside abandoned mine openings in Colorado since 1955.
A man fell to his death in April 1970 after he stepped over a snow-covered shaft at the Glory Mine in Gilpin County. An 11-year-old boy died in December 1986, when he fell into a mine shaft while skiing out of bounds on Aspen Mountain. Three kids, ages 15, 16, and 17, were 300 feet from the entrance of the Bookcliffs Mine in Mesa County when they died from a lethal concentration of carbon dioxide in August 1989. The steel door to the mine was previously locked but had been vandalized a few months earlier, allowing entry.
“That number on the website is likely, I can assure you, an undercount,” he said. “The last time it was updated was probably 15 years ago.”
A very long to-do list
After Nelson’s death, the state put construction fencing around the site, but the abandoned shaft won’t be closed until next year.
Snow will hinder state workers’ work to secure the shaft, but also their ability to conduct an endangered species evaluation and assess potential impacts of the project to the surrounding environment, Graves said. If the shaft is a home to bats, for example, staff might consider installing a steel grate to allow them to enter and exit, instead of filling the hole with rock.
Funding is always a factor in the type of closure the state decides to install, but it doesn’t affect whether a hazardous opening will be closed, he said.
“Typically, we don’t do an evaluation without the sufficient funding to address it and we certainly have the funding that’s come around to address this feature,” Graves said. Securing an opening costs, on average, around $5,000, but depends on the type of closure, size and area of the mine feature.
The to-do list is long for the team of 20 assigned to secure dangerous mine openings across Colorado.
“Usually our working inventory is one to two years’ worth of projects and so that may be as many as 400 mine features,” he said. “It’s a lot to do.”
The abandoned mining shaft that Nelson fell into was on public land, but the fear of being held liable for a hiker falling into dangerous structures has led private landowners to forbid public access, including on popular fourteeners.
Owners of the Trinchera Blanca Ranch restricted public access to fourteener Mount Lindsey in the Sangre de Cristo Range in 2021, citing a federal court decision that potentially exposed landowners to lawsuits from hikers and other recreational visitors, but reopened the mountain in March.
Adjustments to the legislation, the Colorado Recreational Use Statute, layered with the waiver that hikers must sign before attempting to hike the mountain, brought “a level of comfort with opening the peak,” a spokesperson for the ranch, which is owned by billionaire conservationist Louis Bacon, previously told The Sun.
Under the law, hikers are allowed to sue if an injured person could prove that the landowner displayed “willful or malicious failure to guard against a known dangerous condition.”
Another owner of mining land spanning three fourteeners in the Mosquito Range above Alma restricted public access in previous years, citing similar concerns that hikers injured in the old mining structures on the peaks could sue him. John Reiber sold off 289 acres atop Mount Democrat in 2023 to The Conservation Fund who then transferred the land to the U.S. Forest Service, ending the thorny access issue on the popular Decalibron Trail.
The deal did not include the Reiber’s property across Mount Lincoln, though, and he still requires that all hikers scan QR codes and sign liability waivers promising not to sue him if they are injured on his property.
A dedicated team of rescuers, the Colorado Front Range Mine Rescue, trains year-round to assist small mines in case something goes wrong with their miners underground, but is also available for emergencies involving the public near abandoned mines, president David Hunsicker said.
“We understand the needs that Colorado has abandoned mines and things do happen, so we’ve put our services out there. So if something were to go wrong or we have an emergency, we can be used to helping assist a local agency with a rescue or a retrieval,” he said.
When going underground, rescuers bring gas meters, digging tools, and a breathing device that allow them to work for four hours before having to come back out, he said.
But they aren’t called to assist often.
“We’ve been called out maybe three times in 15 years,” Hunsicker said. “It’s a little more rare than you think.”
The state uses historical inventories, through the Bureau of Land Management and U.S. Forest Service, and private landowners, to identify old mining sites. On average, the public informs state officials of about 10 abandoned mining sites a year, Graves said.
“I’d love to see that number increase,” he said.
If you see an inactive mining feature, call the state at 303-866-3567, or email them at drms_info@state.co.us, with the location and GPS coordinates if possible, and a map showing how to access the area.
“We can’t be everywhere all the time, so we really hope, and kind of rely, on the public to provide us information on sites that they are aware of in their wanderings,” Graves said.
“Reach out to us so that we have an idea of what’s going on, so we can address these things before they come up, before they become a problem.”
